You have a mine on your property? Mining gypsum? Something else? Orcs?

That's pretty legit.

Have you posted signs about there being a mine, and the possibility of cave ins and sinkholes? I guess stupid people don't read... which reminds me about the Michigan muskie alliance muskellunge awareness signs that keep getting stolen from Campau lake in alto, mi

I'm pretty confident most people don't know what a musky is, let alone tell the easy differences from a pike.